WELLBORE ANNULAR PRESSURE CONTROL SYSTEM AND METHOD USING ACCUMULATOR TO MAINTAIN BACK PRESSURE IN ANNULUS

• US 20100186960A1
• Filed: 01/28/2010
• Published: 07/29/2010
• Est. Priority Date: 01/29/2009
• Status: Abandoned Application

• Current Assignee: Smith International Incorporated (Schlumberger NV)
• Original Assignee: Smith International Incorporated (Schlumberger NV)
• Inventors: Frink, Phil, Reitsma, Donald G., Couturier, Yawan
• Application Number:
  US12/695,760
• Publication Number:
  US 20100186960A1
• Time in Patent Office: Days
• US Class Current: 166/305.100
• CPC Class Codes: E21B 21/08 Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure valve arrangements therefor E21B21/10
• CPC Class Codes: E21B 21/106 Valve arrangements outside the borehole, e.g. kelly valves valves specifically for maintaining circulation of drilling fluid while connecting or disconnecting tubular joints E21B21/019

Abstract

A system for controlling wellbore annulus pressure during the drilling of a subterranean formation includes a drill string extending into a wellbore. A primary pump is configured for selectively pumping a drilling fluid through the drill string and into an annular space created between the drill string and the wellbore. A fluid discharge conduit is in fluid communication with the annular space for discharging the drilling fluid to a reservoir. A fluid back pressure system is connected to the fluid discharge conduit configured to selectively maintain pressure therein. The fluid back pressure system includes a fluid choke, a back pressure source and an accumulator hydraulically coupled between the back pressure source and the discharge conduit.

Claims

1. A system for controlling wellbore annulus pressure during the drilling of a subterranean formation, comprising:

a drill string extending into a wellbore;

a primary pump for selectively pumping a drilling fluid through the drill string and into an annular space created between the drill string and the wellbore;

a fluid discharge conduit in fluid communication with the annular space for discharging the drilling fluid to a reservoir; and

a fluid back pressure system connected to the fluid discharge conduit configured to selectively maintain pressure therein, the fluid back pressure system including a first controllable fluid choke, a fluid back pressure source and an accumulator hydraulically coupled between the back pressure source and the discharge conduit.

2. The system of claim 1 wherein the back pressure source comprises a secondary pump.

3. The system of claim 2 further comprising a pressure control switch connected to the secondary pump and configured to switch the secondary pump off when a fluid side of the accumulator is charged to a selected fluid pressure.

4. The system of claim 1 wherein the back pressure source comprises the primary pump.

5. The system of claim 1 further comprising a second controllable fluid choke disposed hydraulically between the accumulator and the discharge conduit.

6. A method for controlling fluid pressure in a wellbore annulus, comprising:

pumping drilling fluid through a drill string extended into a wellbore, out the bottom of the drill string and into the wellbore annulus;

discharging fluid from the annulus through a discharge conduit, the discharge conduit including therein a fluid backpressure system, the backpressure system including a first controllable fluid choke, a fluid backpressure source and an accumulator hydraulically coupled between the fluid backpressure source and the discharge conduit;

controlling the first controllable fluid choke to maintain a selected pressure in the annular space;

operating the fluid backpressure source to charge a fluid side of the accumulator to a selected pressure; and

discharging fluid from the accumulator into the discharge line to maintain the selected pressure in the annulus.

7. The method of claim 6 wherein the fluid backpressure source comprises a drilling rig mud pump.

8. The method of claim 6 wherein the fluid backpressure source comprises an additional pump.

9. The method of claim 6 further comprising controlling a rate of discharge of fluid from the accumulator.

10. The method of claim 9 wherein the controlling discharge from the accumulator is performed by operating a second controllable fluid choke hydraulically disposed between the accumulator and the discharge conduit.